This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. The study will test whether it works better to give people with hemophilia their replacement clotting factor (Advate) on a routine (prophylactic) basis rather than giving it only when there is an acute bleeding incident. This study will also compare two different dosing schedules for the prophylactic regimen and assess the efficacy of these regimens by monitoring bleeding episode rates and quality of life questionnaires.